It sounds too me like she carries around all these unresolved issues. She keeps bringing up the past because it is something that is still bothering her to this day.
That is not right to bring the kids into things because you helped raise them and you both also have a son together.
The problems that you both had should be discussed together and none of the children should be brought into the relationship.
Yes, very true in what you are saying. She is trying to make excuses why she had an affair basically blaming your sex life. But sex is not everything that makes up a relationship and cheating is never right no matter what issues you have in a relationship.
What she did was wrong and you do not cheat, you stay in the relationship and work things out. She is trying to justify her actions on what she did but you can't. What she did was wrong.
You need to clearly tell her that this marriage is over and the past is the past. You need to tell her what she did was wrong and the children should not be involved in this.
You need to to tell her that we still have a child together and that will never change. Explain that you are going to raise your child and move on from this relationship.
Explain that you are divorced now and the problems that we had when we were married are over and you are no longer discussing them. Tell her you moved on you are with someone else. I am no longer in your life only for our child.
You do not deserve to have the past be brought up all the time when this relationship is over. Explain that she should have told you all these things before she did what she did. Tell her their is no excuse for her actions no matter how she tries to justify them. Tell her you are trying to move on.
You need to tell her how you feel.
She has told you about everything wrong when it comes to the relationship and the sexual issues. Tell her how you feel about what she has done.
Right now she has taken over the past relationship by blaming you in some way for her actions. But what she did there is no excuse for. She was married, she cheated, she is wrong. A marriage is about two people working together. When you . have issues you discuss them, you do not cheat, get divorced and see someone else. then blame you for her cheating because there were sexual problems. These needed to be discussed then, not when the relationship is over. You need to clearly state that this relationship is over, we are no longer intimate, so you need to move on from the past tell her, explain she is with someone else, you are moving on and that you will be there to raise your child.
You are still and always will the father of your child.
Tell her that the past is the past you both are divorced the relationship is over, you no longer have to listen about what has gone wrong in the relationship. Tell her that the only thing you will discuss is your child with her. You can't keep listening to the past mistakes when the marriage has been over for a long time.
She needs to move on now.